Reworking of these workpieces occurs mostly through a hammering of the workpieces by hand or through an overexpanding beyond the straightened position, so that the workpiece after springing back has the desired straightness. Such a hammering or overexpansion demands great skill and experience. Material destructions, for example breakage or tears, will occur due to excessive mechanical working. In addition, these operations are very difficult and the magnitude of waste can be very high.
Reworking can also be done by exposing the curved tool to a local heating up operation, which results in an expansion at said point. However, this heating up has the disadvantage, that the workpiece loses its hardness. Also this method of working is very difficult and only experienced workers achieve satisfactory results.
The purpose of the invention is to provide a reworking method and an apparatus to perform the method, which permits an economical surface working or reworking of a workpiece without influencing the material characteristics and nominal measurements.
Surprisingly it has been found that a grouping of high frequency strikes or blows directed with a strike bolt having a curved point against a workpiece surface, preferably distributed over the particular surface to be treated, results in the desired result.
For reworking, the strikes are applied to the inner side of the curvature.
To carry out this method, an apparatus is suitable, which is inventively characterized by a column, on which is movably and adjustably arranged a strike hammer device for applying a continuous grouping of strikes by means of a strike bolt having a curved point, and a rigid table for supporting the workpiece in the path of movement of the strike bolt.
It is preferable to construct the table which supports the workpiece directly as a measuring table, and an absolute measurement is not necessary. It is sufficient, to perform a comparison measurement, since the goal of the invention is to end up with a flat and rectilinear extent of the surface of the workpiece.
The table can therefore be flat, so that an inexactness can be recognized through a tilting of the workpiece or through an air gap.
As a comparison measuring device a flat plate is suitable, which is constructed with discharging air channels, these air channels being arranged in alignment and at equal distance, each air channel being under pneumatic pressure and is connected to an indicating device which indicates the pressure drop as a result of the exiting gas. Each air channel can be connected to each one U-shaped bent tube, which on its inside is filled partly with a preferably colored liquid and the one end of which is closed off air-tight and the other end of which is connected between the ends of a line from a gas source to the air channel.
The invention will be discussed more in detail with reference to the drawing, in which one exemplary embodiment of an apparatus for reworking and comparison measuring of a workpiece is shown.